An Associated Press analysis found that there are thousands of laws, rules and regulations at the local, county, state and federal levels. The laws and rules vary by state, and even within states, according to a 2011 compilation of state gun laws by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

These laws and regulations govern who can carry a firearm, what kind of firearm is legal, the size of ammunition magazines, and more. In some places, a person can buy as many guns as desired.

Not only can people acquire military-style assault weapons, they can also get gangster-style Tommy guns, World War II-era bazookas and even sawed-off shotguns.

"If you regulate something on the local or state level, you are still a victim to guns coming into other localities or states," said Laura Cutilletta, a senior staff attorney at the California-based Law Center to Prevent Gun Violence.

In California, most guns come from Nevada, where there is almost no regulation of firearms, Cutilletta said, and in Arizona, gun owners don't need a permit.

President Barack Obama earlier this month announced a $500 million plan to tighten federal gun laws. The December shooting massacre in Newtown, Conn., that killed 20 children and six adults at an elementary school launched the issue of gun control policy to a national focus not seen in decades.

Obama is urging Congress to pass new laws, some of which would set a minimum standard for the types of firearms and ammunition that are commercially available. Sen. Dianne Feinstein, D-Calif., on Thursday said she was introducing a new assault weapons ban.

The powerful gun lobby says the problem lies in enforcement of existing laws.

"Which begs the question: Why are we putting more laws on the books if we're not enforcing the laws we already have on the books?" said Andrew Arulanandam, spokesman for the National Rifle Association.

New gun laws will face tough opposition in Congress, particularly from members who rely on the NRA during election campaigns. The NRA contributed more than $700,000 to members of Congress during the 2012 election cycle, according to the Center for Responsive Politics.

Recognizing the opposition in Congress, states already are passing their own new gun laws while officials from some states are promising to ignore any new federal mandates. As the national debate on gun control and Second Amendment rights escalates, the terms being used won't mean the same thing everywhere, due to the thousands of laws, rules and regulations across the country.